Traffic accidents are the leading cause of death for people age 45 and younger in China. But what looked like a drop in traffic deaths reported by police over a recent five-year period doesn't reflect reality, suggests the new study, partly funded by the Chinese government.

The findings are important for China, where an increasing number of people are able to afford to buy cars, with many hitting the streets with little more than cursory training.

Drivers often whip around corners even when pedestrians have the right of way, and few cyclists wear helmets. Impatient taxi drivers drape unbuckled seat belts over their paunches if they think traffic police are looking.

"The reason the government should pay attention is that road deaths are a crucially important and unrecognized problem, and in order to be able to measure progress one needs good data," the study's co-authors, Timothy Baker and Susan Baker, professors at the Johns Hopkins Bloomberg School of Public Health in the US, said in an e-mail.

The China Automotive Technology Research Center said last year that traffic deaths dropped 28 percent from 2004 to 2009, with 67,000 deaths in 2009.

But American and Chinese researchers questioned how such numbers could be accurate. In 2006, they note in the study, the 6.8 per 100,000 death rate reported by China was far lower than in other developing and middle-income countries, which typically register around 21.5 and 19.5 deaths per 100,000, respectively.

The study's researchers, from Johns Hopkins and China's Central South University, compared police data with death certificates from doctors logged between 2002 and 2007. They found that police statistics showed a 27 percent decrease in traffic fatalities, while those recorded on death certificates increased by 8 percent.

In 2007, for instance, police logged 81,649 deaths, compared to 221,135 listed on death certificates, said the study, whose findings were released this week.

Death registration data are collected by the Health Ministry but aren't used to calculate road-death estimates. Police reports are used because traffic safety falls under the Public Security Ministry's Road Traffic Bureau.

The World Health Organization's representative in China, Michael O'Leary, said the WHO and the Chinese government are working to improve the quality of their numbers. The WHO was not involved in the study.

"Regardless of the data, I think everybody agrees there's too many injuries and deaths from road collisions globally," O'Leary told The Associated Press on Thursday. "China is such a rapidly growing developing country that it's difficult to keep up."